(1) Field of the Invention
The present invention relates to a simple and advantageous process of producing potassium tetrafluoro aluminate and more particularly to a process of producing potassium tetrafluoro aluminate of a melting point not exceeding 575.degree. C.
(2) Description of the Prior Art
The conventional technical methods of producing potassium tetrafluoro aluminate comprise reacting the hydrate of alumina, hydrofluoric acid, and potassium hydroxide. After separating the solid reaction product from the mother liquor, there is obtained a reaction product which does not melt below 620.degree. C. Such a product can be used only for certain specific purposes. In order to increase the yield when proceeding according to the known processes, the potassium hydroxide is usually added in an excess up to about 20% of the theoretically required amount. Thereby, however, no substantial change in the melting point of the reaction product is achieved.
It is possible to produce potassium tetrafluoro aluminate of a lower melting point by concentrating by evaporation a suspension obtained by combining stoichiometric amounts of the reaction components. This process, however, is very expensive due to the high energy requirements.
Another technical process of producing potassium tetrafluoro aluminate which melts below 575.degree. C. without any unmelted residue, consists in melting together comminuted potassium fluoride and aluminum fluoride at a temperature above 600.degree. C. and grinding the resulting solidified melt. This process also demands high energy requirements. Moreover, the resulting reaction product frequently contains undesirable impurities.